The present invention relates to a brushless motor having magnetic poles. In particular, the present invention relates to a brushless three-phase motor having permanent magnets, comprising a rotor which can rotate around a rotation axis and has a specific number of magnetic poles, and a stator which is arranged coaxially with respect to the rotation axis and the rotor. The stator has three stator teeth for each two poles, which stator teeth are distributed uniformly around the rotation axis. The stator teeth form slots which are arranged between them. The distance between the center points of mutually adjacent stator teeth defines a slot pitch.
As a rule, the stator teeth are distributed in periodic groups depending on the number of motor phases. Each individual tooth is provided with a concentric winding (single-tooth winding).
FIG. 1 shows such a motor from the prior art, wherein the stator comprises nine stator teeth, which are subdivided into three periodic groups. The stator is arranged concentrically around the rotor. The rotor is provided with six magnetic poles, which each extend along one slot pitch. Furthermore, each magnetic pole has a radius of curvature which is smaller than the radius of curvature of a cylindrical surface which encloses the rotor itself, in order that the induced electromotive force is as sinusoidal as possible.
Brushless motors of the type described above have a defect as a result of the so-called cogging torque, to correct or reduce which, various technical solutions have been used, although these have led to various further defects, such as: loss of the magnetic flux when using the same active material; design complications; airborne noise and oscillations arising from geometric discontinuities; harmonics in the electromotive force which have a negative effect on the resultant active torque; and contradictory geometries/shapes arising from the requirement to produce a virtually sinusoidal electromotive force.